It is well known in the art to use valves, hydraulic or pneumatic, to control and direct the flow of a fluid between two or more locations. When more than two locations are considered, the multistage valve is usually controlled by at least two different actuators, either automatic or under manual operation, that control respective stages.
Furthermore, because of the use of automatic actuators, the effect is typically only a closed-open type configuration. In order to get either a proportional (continuous or progressive) closing or opening operation or a precise control operation, high accuracy from the actuator as well as precision machining of the different valve components are required which significantly increases the cost of such a valve. Moreover, a high precision valve typically requires the assembly of a large quantity of pieces which further increase the cost thereof. Also, because of the large quantity of pieces, the adjustment or calibration of such a valve is usually complex and needs to be performed by highly skilled technicians.
Even more precision is required when such a valve operates with a relatively low-pressure fluid.
Accordingly, there is a need for an improved multistage proportional valve with a simple configuration.